import java.util.HashSet;
import java.util.Set;

public class setTest {
    public static void main(String[] args) {
        Set<Integer> s =    new HashSet<>();
        s.add(66);
        s.add(55);
        s.add(55);
        s.add(88);
        s.add(77);
        System.out.println(s);

        student222 student222 = new student222();
        student222 student111 = new student222();
        System.out.println(student111.hashCode()); // 相同
        System.out.println(student111.hashCode()); // 相同
        System.out.println(student222.hashCode()); // 相同2
        System.out.println(student222.hashCode()); // 相同2
    }
}
